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Posted to commits@trafodion.apache.org by hz...@apache.org on 2018/04/25 16:27:11 UTC
[1/4] trafodion git commit: [TRAFODION-3042] RAND() function is not
always random
Repository: trafodion
Updated Branches:
refs/heads/master dd051ea60 -> 06d38d5d3
[TRAFODION-3042] RAND() function is not always random
When called without a seed, we use a seed based on the
system timestamp. The random generator we use generates similar
output values for seeds that are close together. Adding another
randomization step to avoid that.
Project: http://git-wip-us.apache.org/repos/asf/trafodion/repo
Commit: http://git-wip-us.apache.org/repos/asf/trafodion/commit/36e21b2c
Tree: http://git-wip-us.apache.org/repos/asf/trafodion/tree/36e21b2c
Diff: http://git-wip-us.apache.org/repos/asf/trafodion/diff/36e21b2c
Branch: refs/heads/master
Commit: 36e21b2c9c722bbcb551c35a761f069811051ea0
Parents: 81fadbc
Author: Hans Zeller <hz...@apache.org>
Authored: Tue Apr 24 21:39:16 2018 +0000
Committer: Hans Zeller <hz...@apache.org>
Committed: Tue Apr 24 21:39:16 2018 +0000
----------------------------------------------------------------------
core/sql/exp/exp_function.cpp | 8 ++++++++
1 file changed, 8 insertions(+)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/trafodion/blob/36e21b2c/core/sql/exp/exp_function.cpp
----------------------------------------------------------------------
diff --git a/core/sql/exp/exp_function.cpp b/core/sql/exp/exp_function.cpp
index a65c120..5ece196 100644
--- a/core/sql/exp/exp_function.cpp
+++ b/core/sql/exp/exp_function.cpp
@@ -5977,6 +5977,14 @@ void ExFunctionRandomNum::initSeed(char *op_data[])
seed_ = x + fraction;
+ // Go through one step of a linear congruential random generator.
+ // (https://en.wikipedia.org/wiki/Linear_congruential_generator).
+ // This is to avoid seed values that are close to each other when
+ // we call this method again within a short time. The eval() method
+ // below doesn't handle seed values that are close to each other
+ // very well.
+ seed_ = (((Int64) seed_) * 1664525L + 1664525L) % 2147483648;
+
if (seed_<0)
seed_ += 2147483647;
if ( seed_ < 1 ) seed_ = 1;
[3/4] trafodion git commit: [TRAFODION-3042] Addressed review comment
Posted by hz...@apache.org.
[TRAFODION-3042] Addressed review comment
Project: http://git-wip-us.apache.org/repos/asf/trafodion/repo
Commit: http://git-wip-us.apache.org/repos/asf/trafodion/commit/80a0113f
Tree: http://git-wip-us.apache.org/repos/asf/trafodion/tree/80a0113f
Diff: http://git-wip-us.apache.org/repos/asf/trafodion/diff/80a0113f
Branch: refs/heads/master
Commit: 80a0113f4fd267a367d58a589f95dd33400cbd8a
Parents: 4f83472
Author: Hans Zeller <hz...@apache.org>
Authored: Tue Apr 24 23:22:26 2018 +0000
Committer: Hans Zeller <hz...@apache.org>
Committed: Tue Apr 24 23:22:26 2018 +0000
----------------------------------------------------------------------
core/sql/exp/exp_function.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/trafodion/blob/80a0113f/core/sql/exp/exp_function.cpp
----------------------------------------------------------------------
diff --git a/core/sql/exp/exp_function.cpp b/core/sql/exp/exp_function.cpp
index 109e06d..70eb59c 100644
--- a/core/sql/exp/exp_function.cpp
+++ b/core/sql/exp/exp_function.cpp
@@ -5953,7 +5953,7 @@ void ExFunctionRandomNum::initSeed(char *op_data[])
// we call this method again within a short time. The eval() method
// below doesn't handle seed values that are close to each other
// very well.
- seed_ = (((Int64) seed_) * 1664525L + 1664525L) % 2147483648;
+ seed_ = (((Int64) seed_) * 1664525L + 1013904223L) % 2147483648;
if (seed_<0)
seed_ += 2147483647;
[2/4] trafodion git commit: [TRAFODION-3042] Switch to
nanosecond-resolution time
Posted by hz...@apache.org.
[TRAFODION-3042] Switch to nanosecond-resolution time
Getting ready for the day where we can do two RAND() calls
in a microsecond - hopefully soon :-)
Project: http://git-wip-us.apache.org/repos/asf/trafodion/repo
Commit: http://git-wip-us.apache.org/repos/asf/trafodion/commit/4f834729
Tree: http://git-wip-us.apache.org/repos/asf/trafodion/tree/4f834729
Diff: http://git-wip-us.apache.org/repos/asf/trafodion/diff/4f834729
Branch: refs/heads/master
Commit: 4f834729efa2c9ae74922f1f32226a29b6f8d7d0
Parents: 36e21b2
Author: Hans Zeller <hz...@apache.org>
Authored: Tue Apr 24 22:01:37 2018 +0000
Committer: Hans Zeller <hz...@apache.org>
Committed: Tue Apr 24 22:01:37 2018 +0000
----------------------------------------------------------------------
core/sql/exp/exp_function.cpp | 42 ++++++--------------------------------
1 file changed, 6 insertions(+), 36 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/trafodion/blob/4f834729/core/sql/exp/exp_function.cpp
----------------------------------------------------------------------
diff --git a/core/sql/exp/exp_function.cpp b/core/sql/exp/exp_function.cpp
index 5ece196..109e06d 100644
--- a/core/sql/exp/exp_function.cpp
+++ b/core/sql/exp/exp_function.cpp
@@ -51,6 +51,7 @@
#include <string.h>
#include <stdio.h>
#include <uuid/uuid.h>
+#include <time.h>
#include "NLSConversion.h"
#include "nawstring.h"
@@ -5937,45 +5938,14 @@ void ExFunctionRandomNum::initSeed(char *op_data[])
// Pick an initial seed. According to the reference given below
// (in the eval function), all initial seeds between 1 and
- // 2147483646 are equally valid. So, we just need to pick one
+ // 2147483647 are equally valid. So, we just need to pick one
// in this range. Do this based on a timestamp.
+ struct timespec seedTime;
- // Use ex_function_current to get timestamp.
- //
- char currBuff[32];
- char *opData[1];
- opData[0] = currBuff;
- ex_function_current currentFun;
- currentFun.eval(&opData[0], 0, 0);
+ clock_gettime(CLOCK_REALTIME, &seedTime);
- // Extract year, month, etc.
- //
- char *p = currBuff;
- short year = *((short*) p);
- p += sizeof(short);
- char month = *p++;
- char day = *p++;
- char hour = *p++;
- char minute = *p++;
- char second = *p++;
- Lng32 fraction = *((Lng32*) p);
-
- // Local variables year, ..., fraction are now initialized.
- // From the values of these variables, generate a seed in the
- // desired range.
-
- Lng32 x = year * month * day;
- if (hour) x *= hour;
- p = (char*) &x;
-
- assert(sizeof(Lng32)==4);
-
- p[0] |= (second<<1);
- p[1] |= (minute<<1);
- p[2] |= (minute<<2);
- p[3] |= second;
-
- seed_ = x + fraction;
+ seed_ = (Int32) (seedTime.tv_sec % 2147483648);
+ seed_ ^= (Int32) (seedTime.tv_nsec % 2147483648L);
// Go through one step of a linear congruential random generator.
// (https://en.wikipedia.org/wiki/Linear_congruential_generator).
[4/4] trafodion git commit: Merge [TRAFODION-3042] RAND() function is
not always random PR-1539
Posted by hz...@apache.org.
Merge [TRAFODION-3042] RAND() function is not always random PR-1539
Project: http://git-wip-us.apache.org/repos/asf/trafodion/repo
Commit: http://git-wip-us.apache.org/repos/asf/trafodion/commit/06d38d5d
Tree: http://git-wip-us.apache.org/repos/asf/trafodion/tree/06d38d5d
Diff: http://git-wip-us.apache.org/repos/asf/trafodion/diff/06d38d5d
Branch: refs/heads/master
Commit: 06d38d5d3d2eedf542b5fc4b231575c7c32a698d
Parents: dd051ea 80a0113
Author: Hans Zeller <hz...@apache.org>
Authored: Wed Apr 25 16:07:16 2018 +0000
Committer: Hans Zeller <hz...@apache.org>
Committed: Wed Apr 25 16:07:16 2018 +0000
----------------------------------------------------------------------
core/sql/exp/exp_function.cpp | 50 +++++++++++---------------------------
1 file changed, 14 insertions(+), 36 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/trafodion/blob/06d38d5d/core/sql/exp/exp_function.cpp
----------------------------------------------------------------------